The effect of the presence of trace elements in wort has been recognized for many years. It is well known that various metals can affect the physical stability of beer. For example, excess copper, tin or iron in the wort can cause beer haze, gushing, off-flavors and discoloration of the finished product.
Present day market conditions demand long shelf lives for beer. Therefore, brewers have been concerned with controlling the factors that can alter the physical stability of the packaged product. One approach used by many brewers to insure physical stability has been to reduce the inorganic ion content of wort.
Market conditions also have led to the gradual abandonment of traditional brewing practices and the implementation of more efficient equipment and processes. The more effective removal of trub and the use of hop extracts in place of crude hops also has lead to a reduction of the amount of inorganic ions in the wort. As a result, worts now often contain a concentration of zinc and other metal ions which falls far short of the necessary minimum levels.
Recent studies have proven that zinc is an important element that enhances yeast growth, promotes vigorous fermentation and reduces flavor defects The requirements of yeast for adequate supplies of zinc and other trace elements are not surprising in view of the large number of enzymes involved in crucial metabolic pathways that require divalent cations as co-factors. For example, the yeast enzyme alcohol dehydrogenase, which converts acetaldehyde to ethanol, requires four atoms of zinc; two to hold the molecule together and the other two to confer activity to the enzyme. A zinc deficiency can lead to a loss in the activity of this enzyme and have severe repercussions on primary and secondary metabolic pathways.
For many years, yeast supplements were used in the brewing process as a primary source of zinc for yeast. Recently, however, because of the growing popularity of additive-free brewing, these sources of zinc have been eliminated from the production of many worts,
There is a need for an additive-free process of supplementing the wort with zinc and the other desirable trace elements needed to enhance yeast growth, to insure vigorous fermentations and to reduce to a minimum flavor defects.